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Fact Sheets

MISSE: Testing materials in space

The Materials International Space Station Experiment (MISSE),
the first experiment mounted externally on the International Space
Station (ISS), will investigate the effects of long-term exposure
of materials to the harsh space environment. MISSE will evaluate
the performance, stability, and long-term survivability of
materials and components planned for use by NASA, commercial
companies and the Department of Defense (DOD) on future Low Earth
Orbit (LEO), synchronous orbit, and interplanetary space missions.
The Long Duration Exposure Facility (LDEF), which was retrieved in
1990 after spending 69 months in LEO, revealed that space
environments are very hostile to many spacecraft materials and
components. Atomic oxygen, which is the most prevalent atomic
species encountered in LEO, is highly reactive with plastics and
some metals causing severe erosion. There is also extreme
ultraviolet radiation due to the lack of an atmospheric filter.
This radiation deteriorates and darkens many plastics and coatings.
The vacuum in space also alters the physical properties of many
materials. Impacts of meteoroids and orbiting man-made debris can
damage all materials exposed in space. The combined effects of all
of these environments on spacecraft can only be investigated in
space. On Earth, a material can only be subjected to one
environment at a time. MISSE will evaluate materials currently
being used and those planned for use in future space missions.

Materials Tested

There are about 1,500 samples being tested on the MISSE project.
Samples range from components such as switches, sensors, and
mirrors to materials like polymers, coatings, and composites. There
are also biological materials such as seeds, spores, and various
types of bacteria being evaluated. Each material on the mission had
to be individually tested in the laboratory prior to being
selected. The ultimate test for the materials is when they are
exposed to the space environment. In the laboratory, each material
can only be exposed to one particular simulated environment at a
time. In space, they are exposed to all of the environments at
once. Besides testing new materials, MISSE will also be addressing
questions concerning current materials, such as those being used in
communication satellites which are being plagued with premature
failures of the solar cell power arrays. New generations of solar
cells with longer expected lifetimes will also be tested.

MISSE will also be testing coatings used to control heat
absorption and emission temperatures of satellites. The hostile
environment of space limits the useful life of currently used
coatings. New coatings, which are expected to be much more stable
in space and therefore have longer useful lives, will be tested.
MISSE will also address a major problem for a manned exploration of
Mars: shielding the crew from the very energetic cosmic rays found
in interplanetary space. New concepts for lightweight shields will
be tested on MISSE. Ultra-light membrane structures are planned for
solar sails, large inflatable mirrors and lenses. The effects of
micrometeoroid impacts on these materials will also be
investigated.

Langley Materials

Some of the space polymers to be tested on MISSE such as Triton
Oxygen Resistant were developed by John W. Connell of
Langleys Advanced Materials and Processing Branch. Colorless
polyimide films known as CP1 and CP2, created by former Langley
employee Anne K. St. Clair, are also being tested on MISSE. Langley
is world famous for the development of space-tailored polymers.
Before polymers can be used in space, they must be tested in
space.

PECs will be attached to the International Space Station
using clamps which lock onto handrails outside ISS.

Deploying MISSE

The materials selected for the mission are placed into four
suitcase-like Passive Experiment Containers (PECs). The PECs are
used for transporting experiments to and from ISS. During the
STS-105 mission, astronauts Daniel T. Barry and Patrick G.
Forrester will conduct a spacewalk to attach MISSE to handrails
located on the airlock and high-pressure gas tanks. Once attached,
the astronauts will open the cases and expose MISSEs
materials to the space environment.

After a year of exposure in space, MISSE will be retrieved in
the same manner it was deployed. Tests will be conducted to
determine the effects of its exposure. These tests will determine
which materials are strong enough to survive in space. MISSE will
provide significant new materials and component technologies to
help the U.S. maintain its space superiority.

Participants in MISSE

The MISSE Project is a cooperative endeavor managed by NASA
Langley Research Center. Participants include: Johnson Space
Center, Marshall Space Flight Center, Glenn Research Center, the
Materials Laboratory at the Air Force Research Laboratory, and the
Boeing Phantom Works. Shuttle/ISS MISSE integration is performed by
the USAFs DoD Space Shuttle and ISS Payload Integration
Directorate.

For more information on MISSE, visit <http://misse1.larc.nasa.gov/>
on the Internet or contact NASA Langley Research Center Office of
Public Affairs, Mail Stop 115, Hampton, VA 23681-21999,
757-864-5036.